Blue‐Light‐Absorbing Thin Films Showing Ultralong Room‐Temperature Phosphorescence

Abstract

population of the excited triplet via a spinforbidden intersystem crossing from singlet to triplet. Moreover, the excited triplet can be quenched quite easily by molecular oxygen or deactivated through nonradiative pathways ( Figure 1A). In the literature, two main approaches have been developed to overcome those issues and achieve persistent RTP in aerated atmosphere. In any case, the phosphors must be contained in a rigid environment, inducing a restriction of molecular motion, be it a crystalline structure [11][12][13] or the use of an external host trapping the luminophore in the amorphous phase. [14,15] In both systems, much progress has been achieved, and efficient materials have been developed reporting long-lasting phosphorescence and high phosphorescence quantum yield. In 2017, Shoji et al. revealed the exceptional phosphorescence properties of a series of simple crystalline arylboronic esters, with lifetimes up to 1.73 s, which is-to the best of our knowledge-one of the longest values ever reported for metal-free organic phosphors. [16] Earlier this year, Su et al. designed an organic molecule that is able to participate in multiple hydrogen bondings. After dispersion into polyvinyl alcohol (PVA) to create drop-coating thin films and long irradiation under strong UV light (65 min, 254 nm), an intense phosphorescence (Φ p up to 11.23%) associated with a long lifetime (up to 0.71 s) could be observed at room temperature in aerated atmosphere. In fine, these films could be used to print and encode information. [17] These examples, as for most of the studies reporting URTP pure organic systems described in the literature, work only with excitation in the UV range to trigger the phosphorescence response. This represents a clear limitation and makes these materials hardly suitable for potential mass commercial purpose. The only exception has been reported by Huang and co-workers in 2017. [18] In this work, the authors describe the rational design of new phosphorescent organic crystalline powders, characterized by very long emission lifetimes (up to 0.84 s), due to the derivatives ability to form H aggregates. For one crystalline target with absorption strength ranging up to 450 nm, phosphorescence could be obtained after excitation with a commercial white light-emitting diode (LED). But the long-term stability of such crystalline structures is unclear and unreliable, and the elaboration of thin films from such materials can be laborious, which makes them impractical for the development of smart tags or security devices.The development of organic materials displaying ultralong room-temperature phosphorescence (URTP) is a material design-rich research field with growing interest recently, as the luminescence characteristics have started to become interesting for applications. However, the development of systems performing under aerated conditions remains a formidable challenge. Furthermore, in the vast majority of molecular examples, the respective absorption bands of the compounds are in the near ultraviolet (...

Ultralong room-temperature phosphorescence of a solid-state supramolecule between phenylmethylpyridinium and cucurbit[6]uril

“…Information encryption and anti-counterfeiting are of great signicance and have received enormous attention in this information era. [43][44][45][46][47][48][49] On the basis of distinct lifetime and robust phosphorescence properties of these complexes, a triple encoding model was fabricated. As illustrated in Fig.…”

A Synergistic Enhancement Strategy for Realizing Ultralong and Efficient Room‐Temperature Phosphorescence

“…Information encryption and anti-counterfeiting are increasingly demanded in this information age. [21] Owning to the diversified RTPp roperties of these polymers,m ultiple encoding for information encryption was fabricated. The digits were written by different polymers in flexible paper, among which the number "54" was written by bright polymer PBr-1, "66" was labeled by long-lived PH-1 and the green black part in "88" was coated with PH-5 ( Figure 4a).…”

Modulation of Thermally Activated Delayed Fluorescence in Waterborne Polyurethanes via Charge‐Transfer Effect

“…In the past decades, purely organicl uminescentm aterials have experienced ab ooming development due to their enormous applicationsi nc hemical sensors, [1][2][3][4] optoelectronics, [5][6][7][8][9] bioimaging [10][11][12][13][14][15] and data storage. [16][17][18][19][20][21] Especially,t hermally activated delayed fluorescence( TADF), [22][23][24][25][26] discovered as the second band of long-lived emission, shows identical contour with the prompt fluorescence( PF) and has been widely used in organic light-emitting diodes (OLEDs). Indeed,T ADF,a lso known as E-type delayedf luorescence, [27] was first reported in 1961.…”

“…In the past decades, purely organic luminescent materials have experienced a booming development due to their enormous applications in chemical sensors, optoelectronics, bioimaging and data storage . Especially, thermally activated delayed fluorescence (TADF), discovered as the second band of long‐lived emission, shows identical contour with the prompt fluorescence (PF) and has been widely used in organic light‐emitting diodes (OLEDs).…”